Parallel power amplifier and associated methods

Abstract

A method and apparatus is provided for use in power amplifiers where multiple parallel power amplifiers provide various output power levels. By selectively enabling and disabling the parallel power amplifiers and combining their outputs, a desired output power can be realized, while choosing a combination of power amplifiers that provide a high efficiency.

1. An RF power amplifier comprising:
 a first power amplifier slice, the first amplifier slice further comprising an amplifier stage having a plurality of switching devices and an output network having reactive components; 
 a second power amplifier slice, the second amplifier slice further comprising an amplifier stage having a plurality of switching devices and an output network having reactive components; 
 wherein outputs of the first and second power amplifier slices are combined to provide an output of the RF power amplifier, and wherein the first and second power amplifier slices can be selectively disabled; and 
 a third power amplifier slice having an output that is combined with the outputs of the first and second power amplifier slices. 
 
   
   
     2. The RF power amplifier of  claim 1 , wherein the outputs of the first and second power amplifier slices are each connected to the output of the RF power amplifier while the slices are disabled. 
   
   
     3. The RF power amplifier of  claim 1 , wherein the power amplifier slices are disabled by connected a dc signal to an input of the power amplifier slice to be disabled. 
   
   
     4. The RF power amplifier of  claim 1 , wherein each of the power amplifier slices can be disabled without the use of a switch connected in series between the output network and the load. 
   
   
     5. The RF power amplifier of  claim 1 , wherein the first and second power amplifier slices each have a first impedance as seen by a load while they are enabled, and a second impedance as seen by the load when they are disabled. 
   
   
     6. The RF power amplifier of  claim 5 , wherein the value of the second impedance is dependent on the reactive components of the output network of the disabled slice. 
   
   
     7. The RF power amplifier of  claim 1 , wherein each of the power amplifier slices have the same topology. 
   
   
     8. The RF power amplifier of  claim 1 , wherein the first and second power amplifier slices have different topologies. 
   
   
     9. The RF power amplifier of  claim 1 , wherein the components of each of the output networks of the first and second power amplifier slices are the same sizes. 
   
   
     10. The RF power amplifier of  claim 1 , wherein the components of each of the output networks of the first and second power amplifier slices are different sizes. 
   
   
     11. The RF power amplifier of  claim 1 , wherein each power amplifier slice includes a switching device for disabling its respective slice. 
   
   
     12. The RF power amplifier of  claim 11 , wherein the switching device for disabling its respective slice is coupled between the output of the respective amplifier stage and a bias voltage. 
   
   
     13. The RF power amplifier of  claim 1 , wherein each power amplifier slice has two inputs for receiving a differential input signal. 
   
   
     14. An RF power amplifier for providing power to a load comprising:
 a first power amplifier that can be selectively enabled or disabled, wherein the first power amplifier has a first impedance as seen by the load when the first power amplifier is enabled and a second impedance as seen by the load when the first power amplifier is disabled; 
 a second parallel power amplifier that can be selectively enabled or disabled, wherein the second power amplifier has a third impedance as seen by the load when the second power amplifier is enabled and a fourth impedance as seen by the load when the second power amplifier is disabled, and wherein outputs of the first and second power amplifiers are combined to provide power to the load; and 
 a third power amplifier having an output that is combined with the outputs of the first and second power amplifiers. 
 
   
   
     15. The RF power amplifier of  claim 14 , wherein the second and fourth impedances are not infinite. 
   
   
     16. The RF power amplifier of  claim 14 , wherein values of the second and fourth impedances are dependent upon components in the first and second power amplifiers. 
   
   
     17. The RF power amplifier of  claim 14 , wherein the outputs of the first and second power amplifiers are each connected to the output of the RF power amplifier while the slices are disabled. 
   
   
     18. The RF power amplifier of  claim 14 , wherein the first and second power amplifiers are disabled by connected a dc signal to an input of the respective power amplifier slice to be disabled. 
   
   
     19. The RF power amplifier of  claim 14 , wherein each of the power amplifiers can be disabled without the use of a switch connected in series between the output network and the load. 
   
   
     20. The RF power amplifier of  claim 14 , wherein each of the power amplifiers have the same topology. 
   
   
     21. The RF power amplifier of  claim 14 , wherein the first and second power amplifiers have different topologies. 
   
   
     22. The RF power amplifier of  claim 14 , wherein each power amplifiers includes a switching device for disabling its respective slice. 
   
   
     23. The RF power amplifier of  claim 22 , wherein the switching device for disabling its respective slice is coupled between the output of the respective amplifier stage and a bias voltage. 
   
   
     24. The RF power amplifier of  claim 14 , wherein each power amplifier has two inputs for receiving a differential input signal. 
   
   
     25. A method of providing an amplified signal to an output node in an RF power amplifier comprising:
 providing three or more power amplifiers, each power amplifier having an amplifier stage and a reactive output network; 
 combining outputs of the three or more power amplifiers to provide an amplified signal to the output node of the RF power amplifier; and 
 selectively disabling one or more of the three or more power amplifiers based on a desired output power level, wherein each disabled power amplifier is still connected to the output node. 
 
   
   
     26. The method of  claim 25 , wherein the output of the each respective power amplifier is connected to the output node while the respective power amplifier is disabled. 
   
   
     27. The method of  claim 25 , wherein each power amplifier is disabled by connecting a dc signal to the input of the power amplifier to be disabled. 
   
   
     28. The method of  claim 25 , further comprising using a switching device for disabling each respective power amplifier. 
   
   
     29. The method of  claim 28 , wherein the switching device for disabling its respective power amplifier is coupled between the output of the respective power amplifier and a bias voltage. 
   
   
     30. The RF power amplifier of  claim 1 , wherein the RF power amplifier is a part of a cellular telephone. 
   
   
     31. The RF power amplifier of  claim 14 , wherein the RF power amplifier is a part of a cellular telephone. 
   
   
     32. The method of  claim 25 , further comprising providing a cellular telephone having an antenna, and applying the amplified signal to the antenna of the cellular telephone.